To see a video of an elephant on the move,
visit www.sciencenews.org/elephant_gait
Elephant legs bend like human legs
By Lisa Grossman
Elephants cruise on four-wheel drive and bendy knees
using a gait different from
most quadrupeds, a new
study shows.
Whereas most four-legged
animals use their front legs
to stop and their back legs to
go, elephants split the work
evenly among all their legs.
“There’s no obvious division
of labor,” says study coauthor
Lei Ren of the University
of Manchester in England. All four legs
“work together to achieve the same goals.”
Also, contrary to long-held belief,
elephants’ legs are not stiff columns.
Their joints allow more flex than horses’
do, and are almost exactly as bendy as
human legs. The new work was published
online March 29 in the Proceedings of the
National Academy of Sciences.
A 4-ton elephant named Tantawan crosses a force
platform while cameras capture her movements.
Earlier studies had found that the bigger and heavier an animal, the stiffer its
legs. Ren and his colleagues studied six
Asian elephants to see whether they stand
and walk with their legs straight or bent.
Pillarlike legs mean less work for muscles supporting the animal’s mass, says
coauthor John Hutchinson of the Royal
Veterinary College in Hatfield, England.
The researchers worked with Richard
Lair and expert elephant handlers at the
Thai Elephant Conservation Center in
Lampang, Thailand, to install 16 custom-made force platforms in the ground.
The team placed reflective disks at key
points on the elephants’ bodies and used
seven infrared cameras to record the
elephants’ movements as they walked
or ran over the scales.
The experiments are a technical step
forward, says Herman Pontzer of Wash-
ington University in St. Louis. “It’s always
neat to see this stuff done with elephants,
because it’s so hard to do the work.”
Combining data from the cameras and
the force platforms allowed the scientists
to compute how hard elephants’ muscles
must work during locomotion. The group
found that the muscles provide only one-
third the force that earlier models had
predicted, indicating that elephants’ legs
must be limber enough to act as levers to
propel the animals forward.
Like humans, elephants also tend
to work their muscles harder when
shifting from walking to running, the
team shows.
Caterpillars hang
loose—wet or dry
moths evolved amphibious
life stage in Hawaiian islands
By Susan Milius
They don’t surf, but caterpillars found in
Hawaii are the first insects known to feed
and grow as readily in water as on land.
Other land insects can endure a dunking. And other aquatic ones can survive
a dry spell out of water. But larvae in 12
newly found species in the moth genus
Hyposmocoma can thrive both underwater in rushing streams and exposed to air
on rocks poking out of the water, says evolutionary biologist Daniel Rubinoff of the
University of Hawaii at Manoa.
Besides introducing some
remarkable caterpillars, the
work highlights how islands
influence evolution. Iso-
lated mixes of the relatively
few kinds of creatures that
arrive on islands can come
up with novelties unknown
elsewhere. “Islands are clearly these cru-
cibles of evolution,” Rubinoff says.
The researchers discovered the wet-
dry caterpillars grazing on rocks in
streams, seemingly unfazed by changes
in the water level. In lab studies, the team
showed that the caterpillars don’t have
gills or a way of trapping air bubbles.
Instead, they appear to have another way
to get oxygen directly from the water.
To survive submerged, the caterpillars
need fast-flowing water.
They shelter on the down-
stream sides of rocks and
spin silken tethers to keep
from washing away.
“Interesting, fun and really
quite significant,” Steve
Jordan of Bucknell University in Lewisburg, Pa., says
of the new work.
Hyposmocoma moths live only in the
Hawaiian Islands. Most species in the
genus spend caterpillarhood exclusively on land before flitting away as
full-grown moths. Yet genetic analyses
show that at least three times within
the genus, landlubber lineages have
independently evolved amphibious
caterpillars, Rubinoff and University of
Hawaii colleague Patrick Schmitz report
online March 22 in the Proceedings of
the National Academy of
Sciences.
A Hawaiian caterpil-lar uses a tether to
hold on to a rock in a
fast-flowing stream.
